Compositions for thin-film capacitance device, high-dielectric constant insulating film, thin-film capacitance device, and thin-film multilayer capacitor

ABSTRACT

A thin-film capacitor( 2 ) in which a lower electrode( 6 ), a dielectric thin-film( 8 ), and an upper electrode( 10 ) are formed in order on a substrate( 4 ). The dielectric thin-film( 8 ) is made of a composition for thin-film capacitance devices. The composition includes a bismuth layer-structured compound whose c-axis is oriented vertically to the substrate surface and which is expressed by a formula: (Bi 2 O 2 ) 2+ (A m−1 B m O 3m+1 ) 2− , or Bi 2 A m−1 B m O 3m+3  wherein “m” is an odd number, “A” is at least one element selected from Na, K, Pb, Ba, Sr, Ca and Bi, and “B” is at least one element selected from Fe, Co, Cr, Ga, Ti, Nb, Ta Sb, V, Mo and W. Even if the dielectric thin-film is made more thinner, the dielectric constant is relatively high, and the loss is small. The leak characteristics are excellent, the temperature characteristics of the dielectric constant are excellent, the break-down voltage is improved and the surface smoothness is excellent.

FIELD OF THE INVENTION

The present invention relates to compositions for thin-film capacitancedevice, high-dielectric constant insulating film, thin-film capacitancedevice, and thin-film multilayer capacitor. More particularly, theinvention relates to compositions for thin-film capacitance device usedas dielectric thin-films or so for thin-film capacitance device of everykind, such as condenser or capacitor having conductor-insulator-conductor structure and thin-film capacitance device such as condenseror capacitor wherein said compositions for thin-film capacitance deviceis used as dielectric thin-film.

DESCRIPTION OF THE RELATED ART

In recent years, in the field of Electronic Component, along with thetendencies of higher density and higher integration of electroniccircuit, circuit devices essential to electronic circuit of every kind,such as capacitance device, are desired for more compact body and higherperformance.

For instance, thin-film capacitor using a layer dielectric thin-film, inrespect of integrated circuit with active component such as transistor,is delayed for more compact body. This is a factor of obstruction forrealizing ultrahigh integrated circuit. More compact body for thin-filmcapacitor is delayed because dielectric constant of dielectric materialsused for the thin-film capacitor was low. Accordingly, in order torealize more compact body and relatively high capacitance, the use ofdielectric materials with high dielectric constant is important.

Moreover, in recent years, from the point of capacity density,conventional SiO₂ and Si₃N₄ multilayer films are not good enough to beused for capacitor materials of advanced DRAM(gigabit generation), andmaterials with more higher dielectric constant are being noticed. Inthese materials, the application of TaOx(ε=˜30) has been mainlyconcerned, but other materials have actively come into develop.

On the other hand, as dielectric materials having relatively highdielectric constant, (Ba, Sr)TiO₃(BST) or Pb(Mg_(1/3) Nb_(2/3))O₃(PMN)are known.

Therefore, composing thin-film capacitance device by the use of thesekinds of dielectric materials, more compact body may be expected.

However, when these kinds of dielectric materials are used, by makingthe dielectric film thinner, dielectric constant lowered in some cases.And due to pores that appear on dielectric film by making the dielectricfilm thinner, leak characteristic and break-down voltage deteriorated insome cases. Further, formed dielectric film deteriorated in surfacesmoothing property and change rates of dielectric constant totemperature also tends to deteriorate in some cases. Further, in recentyears, since lead compound such as PMN have large influence onenvironment, high-storage capacitor without lead is desired.

To the contrary, in order to realize more compact body and higherstorage of multilayer ceramic capacitor, the thickness of each layer fordielectric layer is desired to be further thinner as much aspossible(further thinner layer) and the number of laminated layers fordielectric layer at a fixed size is desired to improve as much aspossible(multiple layers).

However, by the use of sheet method(A method comprising the followingsteps. Dielectric green sheet layer is formed such as by doctor blademethod on carrier film using dielectric layer paste. And on thedielectric green sheet layer, internal electrode paste is printed byfixed pattern. Afterwards, these are peeled off and laminated by eachlayer.), when producing multilayer ceramic capacitor, it is impossibleto form thinner dielectric layer than ceramic source material powder.Besides, short or breaking internal electrode problems due to dielectriclayer defects, the dielectric layer was difficult to be further thinner,for instance, 2 μm or less. Moreover, when dielectric layer of eachlayer is further thinner, the number of laminated layers had its limit.Further, by the use of printing method(A method, using screen printingmethod or so, which plural number of dielectric layer paste and internalelectrode paste are alternately printed on carrier film and then thecarrier film is peeled off.), when producing multilayer ceramiccapacitor, the same problem exists.

Due to these causes, producing more compact body and relatively highcapacitance of multilayer ceramic capacitor had its limit.

Accordingly, in order to overcome these problems, various proposes aredone(ex. Japanese Unexamined Patent Publications No. 56-144523, No.5-335173, No. 5-335174, No. 11-214245 and No. 2000-124056).

These publications disclose methods to produce multilayer ceramiccapacitor which dielectric thin-films and electrode thin-films arealternately laminated using thin-film forming method of every kind suchas CVD method, evaporation method or sputtering method.

However, dielectric thin-film formed by the methods described in thesepublications have bad surface smoothing property and when too many ofthe dielectric thin-film are layered, electrode may short-circuit insome cases. Accordingly, the number of laminated layers of at most 12 to13 or so can only be produced, so that even capacitor was capable ofrealizing more compact body, it was not capable of higher capacitance.

Further, as shown in an reference “Particle orientation for bismuthlayer-structured ferroelectric ceramic and application to itspiezoelectric and pyroelectric materials” by Tadashi Takenaka, doctoraldissertation of engineering at Kyoto University(1984), pages 23 to 77 ofArticle 3, it is known that following composition composes a bulkbismuth layer-structured compound dielectric obtained by sinteringmethod; a composition expressed by formula:(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ or Bi₂ A_(m−1)B_(m)O_(3m+3) whereinsymbol m is selected from positive numbers of 1 to 8, symbol A is atleast one element selected from Na, K, Pb, Ba, Sr, Ca and Bi and B is atleast one element selected from Fe, Co, Cr, Ga, Ti, Nb, Ta Sb, V, Mo andW.

However, this article did not describe under which condition(ex. therelation between substrate surface and degree of c-axis orientation) thecompositions shown by abovementioned formula are made furtherthinner(ex. 1 μm or less) in order to obtain the following thin-film. Athin-film which is, when made further thinner, capable of providingrelatively high dielectric constant and low loss, and also superior leakproperty, break-down voltage, temperature characteristic of dielectricconstant and surface smoothness property.

DISCLOSURE OF THE INVENTION

The object of the invention is to provide compositions for thin-filmcapacitance device that are, even made further thinner, capable ofproviding relatively high dielectric constant and low-loss, and alsosuperior leak property, break-down voltage, temperature characteristicof dielectric constant and surface smoothness property, and to providethin-film capacitance device using the compositions. Also, anotherobject of the present invention is, by using these thin-film capacitancedevice compositions as dielectric thin-film, to provide a thin-filmmultilayer capacitor which can give more compact body and relativelyhigh capacitance. Further, the present invention is also to providehigh-dielectric constant insulating film which provide, even madefurther thinner, relatively high dielectric constant and low-loss, alsosuperior leak property, break-down voltage, temperature characteristicof dielectric constant and surface smoothness property.

The inventors of the present invention have earnestly considered ofdielectric thin-film materials used for capacitor and its crystalstructure. As a result, using a bismuth layer-structured compound havingspecific composition, moreover, by orientating c-axis([001] orientation)of the bismuth layer-structured compound vertically to substrate surfaceand composing dielectric thin-film as thin-film capacitance devicecompositions, that is, by forming c-axis orientation film(thin-filmnormal is parallel to c-axis) of bismuth layer-structured compound on tothe substrate surface, it was found that thin-film capacitance devicecompositions and thin-film capacitance device using the compositionscould be provided. The thin-film capacitance device compositions are,even made further thinner, relatively high dielectric constant andlow-loss(low tan δ) can be provided, and also superior leak property,break-down voltage, temperature characteristic of dielectric constantand surface smoothness property. Moreover, by the use of these thin-filmcapacitance device compositions as dielectric thin-film, it was foundthat number of laminated layers can be increased and thin-filmmultilayer capacitor which can give more compact body and relativelyhigh capacitance can be provided. This brought completion of the presentinvention. Furthermore, by using these compositions as high dielectricconstant insulating film, it was found that the compositions can beapplied other than as thin-film capacitance device, which broughtcompletion of the present invention.

Therefore, thin-film capacitance device compositions according to thepresent invention including a bismuth layer-structured compound whosec-axis is oriented vertically to a substrate surface wherein saidbismuth layer-structured compound is expressed by a formula:(Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ or Bi₂A_(m−1)B_(m)O_(3m+3) in whichsymbol “m” is selected from odd numbers, symbol “A” is at least oneelement selected from Na, K, Pb, Ba, Sr, Ca and Bi and symbol “B” is atleast one element selected from Fe, Co, Cr, Ga, Ti, Nb, Ta Sb, V, Mo andW.

“Thin-film” according to the invention is a film for materials whosethickness is about several Å to several μm and formed by thin-filmforming method of every kind. “Thin-film” excludes a thick-film bulkwhose thickness is about several hundreds μm or more and formed bysintering method. Thin-film includes continuous film which covers fixedarea continuously and also intermittent film which covers optionalintervals intermittently. Thin-film may be formed at a part of substratesurface and may also be formed at the entire surface.

The thickness of dielectric thin-film(or high dielectric constantinsulating film) formed by thin-film capacitance device compositionsaccording to the invention is preferably 5 to 1000 nm. When at thisthickness, the present invention is quite effective.

The process of manufacturing thin-film capacitance device compositionsaccording to the invention is not particularly limited but it can bemanufactured by, for instance, using substrates of cubic system,tetragonal system, orthorhombic system, or monoclinic system that are[100] oriented, and forming thin-film capacitance device compositionsincluding a bismuth layer-structured compound which is expressed by aformula: (Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ or Bi₂A_(m−1)B_(m)O_(3m+3)wherein symbol “m” is selected from odd numbers, symbol “A” is at leastone element selected from Na, K, Pb, Ba, Sr, Ca and Bi and symbol “B” isat least one element selected from Fe, Co, Cr, Ga, Ti, Nb, Ta Sb, V, Moand W. In this case, the abovementioned substrate is preferably composedby single crystal.

Thin-film capacitance device of the invention is characterized in athin-film capacitance device wherein lower electrode, dielectricthin-film and upper electrode are formed one by one on the substrate andsaid dielectric thin-film is composed of abovementioned thin-filmcapacitance device compositions of the invention.

Thin-film multilayer capacitor of the invention comprising dielectricthin-films and internal electrode thin-films alternately layered on asubstrate, wherein said dielectric thin-films are composed ofabovementioned thin-film capacitance device compositions of theinvention.

According to the present invention, a bismuth layer-structured compoundwhose c-axis is oriented 100% vertically to the substrate surface, thatis, a bismuth layer-structured compound whose degree of c-axisorientation is 100%, which is particularly preferable. However, thedegree of c-axis orientation may not be complete 100%.

Preferably, said bismuth layer-structured compound whose degree ofc-axis orientation is 80% or more, more preferably, 90% or more, mostpreferably, 95% or more. By improving the degree of c-axis orientation,the effect of the present invention improves.

Preferably, “m” in the formula composing said bismuth layer-structuredcompound is 1, 3, 5 or 7, more preferably, 1, 3 or 5. This is due to theeasiness of manufacturing.

Preferably, said thin-film capacitance device compositions furtherinclude rare-earth element(at least one element selected from Sc, Y, La,Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu).

Preferably said rare-earth element is “Re” and when said bismuthlayer-structured compound is expressed by formula:Bi₂A_(m−1−x)Re_(x)B_(m)O_(3m+3), said x is 0.4 to 1.8, more preferably,1.0 to 1.4. Including rare-earth element decreases leak current andshort ratio, and also Curie temperature can be −100° C. or more to 100°C. or less.

Preferably, said thin-film capacitance device compositions have Curietemperature of −100° C. or more to 100° C. or less.

Preferably, thin-film multilayer capacitor of the invention, saidinternal electrode thin-film is composed of noble metal, base metal orconductive oxide.

At the thin-film capacitance device and thin-film multilayer capacitorof the invention, said substrate may be composed of amorphous material.Lower electrode(or internal electrode thin-film) formed on the substrateis preferably [100] oriented. By forming lower electrode to [100]orientation, c-axis of a bismuth layer-structured compound composingdielectric thin-film formed on the lower electrode can orient verticallyto the substrate surface.

Thin-film capacitance device compositions of the invention anddielectric thin-film as their example are composed of c-axis orientedbismuth layer-structured compound having specific composition.

Thin-film capacitance device compositions composed of c-axis orientedbismuth layer-structured compound having specific composition are, evenwhen film thickness is made further thinner, relatively high dielectricconstant(ex. more than 200) and low loss(tan δ is 0.02 or less) can beprovided. They can also provide superior leak property(ex. leak currentis 1×10⁻⁷ A/cm² or less and short ratio is 10% or less when measured at50 kV/cm electrolytic strength), improved break-down voltage(ex. 1000kV/cm or more), superior temperature characteristic of dielectricconstant(ex. average change rates of dielectric constant to temperatureis within ±500 ppm/° C. at reference temperature of 25° C.) and superiorsurface smoothness property(ex. surface roughness: Ra is 2 nm or less).

Further, thin-film capacitance device compositions according to thepresent invention are, when its film thickness is made further thinner,relatively high dielectric constant can be provided. Moreover, due tothe satisfactory surface smoothness, increasing number of laminatedlayers for dielectric thin-film as said thin-film capacitance devicecompositions is capable. Therefore, by using the thin-film capacitancedevice compositions, thin-film multilayer capacitor that can give morecompact body and relatively high capacitance can be provided.

Further, thin-film capacitance device compositions and thin-filmcapacitance device of the invention are superior in frequencycharacteristic(ex. At specific temperature, ratio of dielectric constantvalue at high frequency domain of 1 MHz and those at lower than theabove frequency domain of 1 kHz is 0.9 to 1.1 in absolute value.) andalso in voltage characteristic (ex. At specific frequency, ratio ofdielectric constant value at measuring voltage of 0.1V and those atmeasuring voltage of 5V is 0.9 to 1.1 in absolute value).

Furthermore, thin-film capacitance device compositions of the inventionare superior in temperature characteristic for electrostaticcapacity(average change rates of the electrostatic capacity totemperature is within ±500 ppm/° C. at reference temperature of 25° C.).

For thin-film capacitance device, but not particularly limited to,conductor —insulator—conductor structured condenser(ex. single layertyped thin-film capacitor or multilayer typed thin-film multilayercapacitor ) or capacitor(ex. such as for DRAM) are exemplified.

For thin-film capacitance device compositions, but not particularlylimited to, dielectric thin-film compositions for condenser ordielectric thin-film compositions for capacitor are exemplified.

High dielectric constant insulating film of the invention is composed ofthe same compositions as thin-film capacitance device compositions ofthe invention. High dielectric constant insulating film of the inventioncan be used as, other than thin-film dielectric film for thin-filmcapacitance device or capacitor, gate-insulating film of semiconductordevice or intermediate insulating film between gate electrode andfloating gate or so.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an example for thin-film capacitor of theinvention,

FIG. 2 is a sectional view of an example for thin-film multilayercapacitor of the invention,

FIG. 3 is a graph of frequency characteristic for capacitor sample ofexample 9,

FIG. 4 is a graph of voltage characteristic for capacitor sample ofexample 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Below, the present invention will be explained based on embodimentsshown in drawings.

First Embodiment

The present embodiment is described by exemplifying a thin-filmcapacitor forming a layer dielectric thin-film as thin-film capacitancedevice. As shown in FIG. 1, thin-film capacitor 2 according to anembodiment of the invention includes substrate 4, and on the substrate4, lower electrode thin-film 6 is formed. On lower electrode thin-film6, dielectric thin-film 8 is formed. On dielectric thin-film 8, upperelectrode thin-film 10 is formed.

Substrate 4 is composed of single crystal with high matched lattice (ex.single crystal of SrTiO₃, MgO or LaAl O₃), amorphous materials(ex.glass, fused quartz or SiO₂/Si) and other materials(ex ZrO₂/Si orCeO₂/Si) or so. Particularly, composed of substrate oriented to such as[100] orientation e.g. cubic system, tetragonal system, orthorhombicsystem, or monoclinic system, are preferable. Thickness of substrate 4is not particularly limited but is about 100 to 1000 μm.

When using single crystal with high matched lattice as substrate 4,lower electrode thin-film 6 is preferably composed of conductive oxide,such as CaRuO₃ or SrRuO₃, or noble metal such as Pt or Ru, morepreferably, [100] oriented conductive oxide or noble metal. When usingsubstrate 4 which is [100] oriented, conductive oxide or noble metalwhich is [100] oriented can be formed on its surface. By composing lowerelectrode thin-film 6 with [100] oriented conductive oxide or noblemetal, degree of orientation to [001], that is, degree of c-axisorientation of dielectric thin-film 8 formed on the lower electrodethin-film 6 increases. This lower electrode thin-film 6 is formed bynormal thin-film forming method. However, it is preferable to be formedby physical vapor deposition method such as sputtering method or pulsedlaser deposition method(PLD) in which temperature of substrate 4 forforming lower electrode thin-film 6 on its surface is preferably 300° C.or more, more preferably 500° C. or more.

Lower electrode thin-film 6 using amorphous materials for substrate 4can be composed of conductive glass such as ITO. When using singlecrystal with high matched lattice as substrate 4, [100] oriented lowerelectrode thin-film 6 can easily be formed on the surface. Due to this,degree of c-axis orientation of dielectric thin-film 8 formed on thelower electrode thin-film 6 tends to increase. However, even usingamorphous materials such as glass for substrate 4, it is possible toform improved degree of c-axis orientation of dielectric thin-film 8. Inthis case, optimization of film formation condition for dielectricthin-film 8 is required.

As other lower electrode thin-film 6, noble metal such as gold(Au),palladium(Pd), Silver(Ag) or their alloys and also base metal such asNickel(Ni), Copper(Cu) or their alloys can be used.

The thickness of lower electrode thin-film 6 is not limited butpreferably 10 to 1000 nm, more preferably 50 to 100 nm or so.

Upper electrode thin-film 10 can be composed of the same material assaid lower electrode thin-film 6. And the thickness can also be thesame.

Dielectric thin-film 8 is an example of thin-film capacitance devicecompositions of the invention, and include bismuth layer-structuredcompound expressed by formula: (Bi₂O₂)²⁺(A_(m−1)B_(m)O_(3m+1))²⁻ or Bi₂A_(m−1)B_(m)O_(3m+3). Generally, bismuth layer-structured compound showsa laminar structure which upper and lower parts of laminar perovskitelayer, which perovskite lattice composed of (m−1) numbers of ABO₃ isranged, are sandwiched by a pair of Bi and O layer. According to thepresent embodiment, the bismuth layer-structured compound improves itsdegree of orientation to [001] orientation, that is, degree of c-axisorientation. Namely, c-axis of bismuth layer-structured compound isvertically oriented to substrate 4 to form dielectric thin-film 8.

In the present invention, it is particularly preferable that the degreeof c-axis orientation for the bismuth layer-structured compound is 100%,however, the degree of c-axis orientation may not be complete 100%.Preferably 80% or more, more preferably, 90% or more, the mostpreferably, 95% or more of the bismuth layer-structured compound may bec-axis oriented. For instance, when bismuth layer-structured compound isc-axis oriented using substrate 4 which is composed of amorphousmaterial such as glass, the degree of c-axis orientation of the bismuthlayer-structured compound may be preferably 80% or more. Moreover, whenbismuth layer-structured compound is c-axis oriented by the use offollowing thin-film forming method of every kind, the degree of c-axisorientation of the bismuth layer-structured compound may be preferably90% or more, more preferably, 95% or more.

In here, the degree of c-axis orientation(F) of bismuth layer-structuredcompound can be found by the formula: F(%)=(P'P0)/(1−P0)×100 . . .(formula 1) wherein P0 is X-ray diffraction strength for c-axis ofperfectly random oriented polycrystal and P is practical X-raydiffraction strength for c-axis. In formula 1, P is ({ΣI(001)/ΣI(hkl)})showing the ratio of the sum ΣI(001) of reflecting strength I(001) from(001) surface to the sum ΣI(hkl) of reflecting strength I(hkl) from eachcrystal surface(hkl) and P0 is the same. However, in formula 1, X-raydiffraction strength P when 100% c-axis oriented is 1. And by formula 1,when perfectly random oriented(P=P0), F=0% and when perfectly orientedto c-axis orientation(P=1), F=100%.

Further, c-axis of the bismuth layer-structured compound signifies anorientation which a pair of (Bi₂O₂)²⁺ layers are connected to, that is,[001] orientation. In this way, as bismuth layer-structured compound isc-axis oriented, dielectric characteristic of dielectric thin-film 8give its full ability. That is, even making thickness of dielectricthin-film 8 further thinner, such as 100 nm or less, relatively highdielectric constant and low-loss(tan δ is low) can be provided. And italso provides superior leak property, improved break-down voltage,superior temperature characteristic of dielectric constant and superiorsurface smoothness property. When tan δ decreases, loss Q(1/tan δ) valueincreases.

In above formula, when symbol “m” is an odd number, it is notparticularly limited. When symbol “m” is an odd number, polarizationaxis to c-axis orientation also exists and in comparison to when “m” isan even number, dielectric constant at Curie point increases. Further,temperature characteristic of dielectric constant, in comparison to when“m” is an even number, tends to deteriorate. However, bettercharacteristic is shown in comparison to those when conventional BST isused. Particularly, by increasing the value of symbol “m”, further riseof dielectric constant can be expected.

In above formula, the symbol “A” is composed of at least one elementselected from Na, K, Pb, Ba, Sr, Ca and Bi. Further, when the symbol “A”is composed of two or more elements, the ratio of those elements isoptional.

In above formula, the symbol “B” is composed of at least one elementselected from Fe, Co, Cr, Ga, Ti, Nb, Ta, Sb, V, Mo and W. Further, whenthe symbol “B” is composed of two or more elements, the ratio of thoseelements is optional.

Dielectric thin-film 8, to said bismuth layer-structured compound,further include at least one element(rare-earth element: Re) selectedfrom Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb andLu is preferable. Substitution amount by rare-earth element varies bythe value of “m”, for instance, when “m”=3 in formula:Bi₂A_(2−X)Re_(X)B₃O₁₂, 0.4≦x≦1.8 is preferable, and 1.0≦x≦1.4 is morepreferable.

Due to substitution of rare-earth element within this range, Curietemperature(temperature of phase transition from ferroelectric toparaelectric) of dielectric thin-film 8 can be kept, preferably, −100°C. or more to 100° C. or less, more preferably −50° C. or more to 50° C.or less. When Curie point is −100° C. to +100° C., dielectric constantof dielectric thin-film 8 increases. Curie temperature can be measuredby DSC(differential scanning calorimetry) or so. Further, when Curiepoint is less than ambient temperature(25° C.), tan δ further decreasesand consequently, the loss Q value further increases.

Further, dielectric thin-film 8, even without rare-earth element Re, issuperior in leak characteristic as following. However, with substitutionof Re, leak characteristic can be further superior.

For instance, in dielectric thin-film 8 without rare-earth element: Re,leak current measured when 50 kV/cm field intensity can be preferably1×10⁻⁷ A/cm² or less, more preferably 5×10⁻⁸ A/cm² or less, further,short ratio can be preferably 10% or less, more preferably, 5% or less.

To the contrary, in dielectric thin-film 8 with rare-earth element Re,leak current measured under the same condition can be preferably 5×10⁻⁸A/cm² or less, more preferably 1×10⁻⁸ A/cm² or less, further, shortratio can be preferably 5% or less, more preferably, 3% or less.

Dielectric thin-film 8 has preferably film thickness of 200 nm or lessand considering higher capacitance, more preferably those of 100 nm orless. Further, the minimum of film thickness, considering insulatingcharacter of film, is preferably about 30 nm.

At dielectric thin-film 8, for instance, surface roughness(Ra) basedupon JIS-B0601 is preferably 2 nm or less, more preferably 1 nm or less.

At dielectric thin-film 8, dielectric constant at 25° C.(ambienttemperature) and 100 kHz(AC20 mV) metering frequency is preferably morethan 200, more preferably 250 or more.

At dielectric thin-film 8, tan δ at 25° C. (ambient temperature) and 100kHz(AC20 mV) metering frequency is preferably 0.02 or less, morepreferably 0.01 or less. Further, the loss Q value is preferably 50 ormore, more preferably 100 or more.

At dielectric thin-film 8, even when frequency at particulartemperature(ex. 25° C.) is changed to high frequency domain, such asabout 1 MHz, dielectric constant change(particularly a decline) issmall. Concretely, for instance, at specific temperature, ratio ofdielectric constant value at high frequency domain of 1 MHz and those atlower than above frequency domain of 1 kHz can be 0.9 to 1.1 in absolutevalue. Namely, frequency characteristic is satisfactory.

In dielectric thin-film 8, even when metering voltage(impressed voltage)at specific frequency(ex. 10 kHz, 100 kHz or 1 MHz) is changed to about5V or so, dielectric constant change is small. Concretely, for instance,at specific frequency, ratio of dielectric constant value at meteringvoltage of 0.1V and those at metering voltage of 5V can be 0.9 to 1.1.Namely, voltage characteristic is satisfactory.

Such dielectric thin-film 8 can be formed by thin-film forming method ofevery kind such as vacuum evaporation method, high frequency sputteringmethod, pulsed laser deposition method(PLD), MOCVD(Metal OrganicChemical Vapor Deposition)method or sol-gel method.

In the present embodiment, by the use of such as substrate oriented tospecific orientation(such as [100] orientation), dielectric thin-film 8is formed. In respect to lower the manufacturing cost, using substrate 4composed of amorphous material is more preferable. Using the dielectricthin-film 8, a bismuth layer-structured compound having specificcomposition is composed by orientating to c-axis. Dielectric thin-film 8and thin-film capacitor 2 using the dielectric thin-film 8 are, evenfilm thickness of dielectric thin-film is made thinner, such as 100 nmor less, relatively high dielectric constant and low loss can beprovided. They can also provide superior leak property, improvedbreak-down voltage, superior temperature characteristic of dielectricconstant and superior surface smoothness property.

Further, these dielectric thin-film 8 and thin-film capacitor 2 are alsosuperior in frequency characteristic or voltage characteristic.

Second Embodiment

The present embodiment is described by exemplifying, as thin-filmcapacitance device, a thin-film multilayer capacitor forming multilayerdielectric thin-film.

As shown in FIG. 2, thin-film multilayer capacitor 20 according to anembodiment of the present invention includes capacitor body 22. Thecapacitor body 22 has multilayer structure which on the substrate 4 a, amultiple number of dielectric thin-film 8 a and internal electrodethin-film 24 and 26 are alternately arranged and protection film 30 isformed to cover dielectric thin-film 8 a arranged at the most externalpart. At both ends of the capacitor body 22, a pair of externalelectrodes 28 and 29 is formed. The pair of external electrodes 28 and29 is electrically connected to each of the exposed edge faces of amultiple number of internal electrode thin-film 24 and 26 that arealternately arranged inside capacitor body 22 to form capacitor circuit.The shape of capacitor body 22 is not particularly limited but normally,rectangular parallelepiped. Further, its size is not limited but forinstance, it has about length of (0.01 to 10 mm)×width of (0.01 to 10mm)×height of (0.01 to 1 mm).

Substrate 4 a is composed of the same material as substrate 4 inabovementioned first embodiment. Dielectric thin-film 8 a is composed ofthe same material as dielectric thin-film 8 in abovementioned firstembodiment. Internal electrode thin-films 24 and 26 are composed of thesame material as lower electrode thin-film 6 and upper electrodethin-film 10 in abovementioned first embodiment. Material of externalelectrode 28 and 29 is not limited and the external electrode iscomposed of conductive oxide such as CaRuO₃ or SrRuO₃; base metal suchas Cu, Cu alloys, Ni or Ni alloys; noble metal such as Pt, Ag, Pd orAg—Pd alloys. The thickness is not limited but for instance, 10 to 1000nm or so. Material of protection film 30 is not limited but composed ofsuch as silicon oxide film or aluminum oxide film. Thin-film multilayercapacitor 20 have first layer of internal electrode thin-film 24 formedon substrate 4 a by masking with metal mask or so, then, dielectricthin-film 8 a formed on the internal electrode thin-film 24 and further,second layer of internal electrode thin-film 26 formed on the dielectricthin-film 8 a. After these processes are repeated for multiple times,dielectric thin-film 8 a arranged at the most external part and oppositeside of the substrate 4 a is covered with protection film 30. And on thesubstrate 4 a, a multiple number of internal electrode thin-film 24 and26 and dielectric thin-film 8 a alternately arranged capacitor body 22is formed. Covering the protection film 30 can decrease the effect ofmoisture in atmosphere on internal part of capacitor body 22. And whenexternal electrodes 28 and 29 are formed at both ends of the capacitor22 by dipping or sputtering or so, internal electrode thin-film 24 ofodd number layers and one side of external electrode 28 are electricallyconnected and continuity is maintained. Then, internal electrodethin-film 26 of even number layers and the other side of externalelectrode 29 are electrically connected and continuity is maintained toobtain thin-film multilayer capacitor 20.

In respect to lower the manufacturing cost, using substrate 4 a composedof amorphous material is more preferable.

Dielectric thin-film 8 a of the present embodiment is, even when madethinner, relatively high dielectric constant can be provided andmoreover, surface smoothness property is satisfactory. Due to these, thenumber of laminated layers can be 20 or more, preferably 50 or more.Accordingly, thin-film multilayer capacitor 20 which may be small-sizedand relatively high capacitance can be provided.

At thin-film capacitor 2 and thin-film multilayer capacitor 20 of theabovementioned present embodiment, when temperature is withintemperature range of at least −55° C. to +150° C., average changerates(Δε) of dielectric constant is preferably within ±500 ppm/° C. (25°C. reference temperature), and more preferably within +250 ppm/° C.

Next, examples wherein the embodiment of the present invention isdescribed more specifically and the present invention will be explainedfurther in detail. Note that the present invention is not limited to theembodiments.

EXAMPLE 1

CaRuO₃ as lower electrode thin-film was epitaxial grown to [100]orientation to form SrTiO₃ single crystal substrate((100)CaRuO₃//(100)SrTiO₃) and was heated to 850° C. Then, on thesurface of CaRuO₃ lower electrode thin-film, with pulsed laserdeposition method, and by the use of SrBi₃Ti₂TaO₁₂(below also as SBTT)sintered body(This sintered body is expressed by formula:Bi₂A_(m−1)B_(m)O_(3m+3) wherein symbol “m”=3, symbol “A₂”=Sr₁, Bi₁ andsymbol “B₃”=Ti₂, Ta₁) as source material, about 200 nm film thickness ofSBTT thin-film(dielectric thin-film) was formed.

When crystal structure of SBTT thin-film was measured by X-raydiffraction(XRD), it was confirmed that this crystal structure was [001]oriented, that is, its c-axis orientation was vertical to the surface ofSrTiO₃ single crystal substrate. Further, surface roughness(Ra) of thisSBTT thin-film was measured by AFM(atomic force microscope, SPI3800;Seiko instruments made) based upon JIS-B0601.

Next, on the surface of SBTT thin-film, 0.1 mm φ Pt upper electrodethin-film was formed by sputtering method and thin-film capacitor samplewas manufactured.

Electric characteristics(dielectric constant, tan δ, the loss Q value,leak current and short ratio) and temperature characteristic ofdielectric constant for the obtained capacitor sample were evaluated.

Dielectric constant(no unit) was calculated from electrostatic capacity,electrode dimension and interelectrode distance of capacitor sample. Theelectrostatic capacity was measured by using digital LCR meter(4274A,YHP made) at capacitor sample, at ambient temperature(25° C.) and 100kHz(AC20 mV) metering frequency.

Tan δ was measured under the same condition as above electrostaticcapacity was measured and the loss Q value was also calculated.

Leak current characteristic(Unit is A/cm²) was measured at 50 kV/cmfield intensity. Short ratio(Unit is %) was determined by measuring 20upper electrodes and calculating the ratio of which short-circuit amongthem.

As temperature characteristic of dielectric constant, at the capacitorsample, measuring dielectric constant under the abovementionedcondition, and when at reference temperature of 25° C., measuringaverage change rates(Δε) of dielectric constant to temperature withintemperature range of −55° C. to +150° C. and calculating temperaturecoefficient(ppm/° C.). The result is shown in table 1.

COMPARATIVE EXAMPLE 1

Except for the use of SrTiO₃ single crystal substrate((110)CaRuO₃//(110) SrTiO₃) which CaRuO₃ as lower electrode thin-filmwas epitaxial grown to [110] orientation, in the same way as example 1,about 200 nm film thickness of SBTT thin-film(dielectric thin-film) wasformed on the surface of CaRuO₃ lower electrode thin-film. When crystalstructure of this SBTT thin-film was measured by X-ray diffraction(XRD),it was confirmed that this crystal structure was [118] oriented, and itsc-axis orientation was not vertical to the surface of SrTiO₃ singlecrystal substrate. Further, in the same way as example 1, surfaceroughness(Ra) of SBTT thin-film and also electric characteristic andtemperature characteristic of dielectric constant for the thin-filmcapacitor sample were evaluated. The result is shown in table 1.

COMPARATIVE EXAMPLE 2

Except for the use of SrTiO₃ single crystal substrate((111)CaRuO₃//(111)SrTiO₃) which CaRuO₃ as lower electrode thin-film wasepitaxial grown to [111] orientation, in the same way as example 1,about 200 nm film thickness of SBTT thin-film(dielectric thin-film) wasformed on the surface of CaRuO₃ lower electrode thin-film. When crystalstructure of this SBTT thin-film was measured by X-ray diffraction(XRD),it was confirmed that this crystal structure was [104] oriented, and itsc-axis orientation was not vertical to the surface of SrTiO₃ singlecrystal substrate. Further, in the same way as example 1, surfaceroughness(Ra) of SBTT thin-film and also electric characteristic andtemperature characteristic of dielectric constant for the thin-filmcapacitor sample were evaluated. The result is shown in table 1.

TABLE 1 Substrate Surface Leak Short Temperature Surface Film RoughnessCurrent Ratio Dielectric Coefficient The Loss Orientation Orientation Ra(nm) (A/cm²) (%) Constant (ppm/° C.) tan δ Q Value Ex. 1 [100] [001] 0.51 × 10⁻⁸ 5 250 <±200 <0.01 >100 Comp. [110] [118] 3 5 × 10⁻⁷ 40 350±1000 >0.01 <100 Ex. 1 Comp. [111] [104] 15 5 × 10⁻⁵ 80 350 ±1000 >0.01<100 Ex. 2

As shown in Table 1, it was confirmed that c-axis orientation film forbismuth layer-structured compound of example 1 is inferior in dielectricconstant, but superior in leak characteristic. Accordingly, not onlyeven thinner-film can be expected but higher capacitance for thin-filmcapacitor can be expected. Moreover, at example 1, it was confirmed thatin comparison to the other orientation directions of comparativeexamples 1 and 2, its temperature characteristic was superior. Further,it was also confirmed that since Example 1 was superior in surfacesmoothness property in comparison to comparative examples 1 and 2, itcan be preferable thin-film material for manufacturing multilayerstructure. Namely, according to example 1, validity of c-axisorientation film for bismuth layer-structured compound was confirmed.

EXAMPLE 2

Except for forming about 35 nm film thickness of SBTTthin-film(dielectric thin-film) on the surface of CaRuO₃ lower electrodethin-film, in the same way as example 1, surface roughness(Ra) of SBTTthin-film and also electric characteristic(dielectric constant, tan δ,the loss Q value, leak current and break-down voltage) and temperaturecharacteristic of dielectric constant for the thin-film capacitor samplewere evaluated. The result is shown in table 2. Further, the break-downvoltage(Unit is kV/cm) was measured by increasing the voltage whenmeasuring leak characteristic.

EXAMPLE 3

Except for forming about 50 nm film thickness of SBTTthin-film(dielectric thin-film) on the surface of CaRuO₃ lower electrodethin-film, in the same way as example 1, surface roughness(Ra) of SBTTthin-film and also electric characteristic and temperaturecharacteristic of dielectric constant for the thin-film capacitor samplewere evaluated. The result is shown in table 2.

EXAMPLE 4

Except for forming about 100 nm film thickness of SBTTthin-film(dielectric thin-film) on the surface of CaRuO₃ lower electrodethin-film, in the same way as example 1, surface roughness(Ra) of SBTTthin-film and also electric characteristic and temperaturecharacteristic of dielectric constant for the thin-film capacitor samplewere evaluated. The result is shown in table 2.

TABLE 2 Film Surface Leak Break-down Thickness Roughness Current VoltageDielectric Temperature The Loss (nm) Ra (nm) (A/cm²) (kV/cm) ConstantCoefficient(ppm/° C.) tan δ Q Value Ex. 2 35 0.5 4 × 10⁻⁷ >1000 250<±200 <0.04 >25 Ex. 3 50 0.5 1 × 10⁻⁷ >1000 250 <±200 <0.02 >50 Ex. 4100 0.5 3 × 10⁻⁸ >1000 250 <±200 <0.01 >100

As shown in Table 2, when film thickness for c-axis orientation film wasmade thinner, it was confirmed that although leak property became littleinferior, surface roughness and dielectric constant did not change.

Further, Reference 1(Y. Sakashita, H. Segawa, K. Tominaga and M. Okada,J. Appl. Phys. 73,7857(1993)) shows the relation between film thicknessof PZT(Zr/Ti=1) thin-film which is c-axis oriented and dielectricconstant. Here, the result is shown that as the film thickness of PZTthin-film was made thinner to 500 nm, 200 nm and 80 nm, the dielectricconstant(@1 kHz) decreased to 300, 250 and 100 respectively. Reference2(Y. Takeshima, K. Tanaka and Y. Sakabe, Jpn. J. Appl. Phys.39,5389(2000)) shows the relation between film thickness ofBST(Ba:Sr=0.6:0.4) thin-film which is a-axis oriented and dielectricconstant. Here, the result is shown that as the film thickness of BSTthin-film was made thinner to 150 nm, 100 nm and 50 nm, the dielectricconstant decreased to 1200, 850 and 600 respectively. Reference 3(H. J.Cho and H. J. Kim, Appl. Phys. Lett. 72,786(1998)) shows the relationbetween film thickness of BST(Ba:Sr=0.35:0.65) thin-film which is a-axisoriented and dielectric constant. Here, the result is shown that as thefilm thickness of BST thin-film was made thinner to 80 nm, 55 nm and 35nm, the dielectric constant(@10 kHz) decreased to 330, 220 and 180respectively.

Moreover, it was confirmed that even with 35 nm film thickness ofexample 2, 1000 kV/cm or more break-down voltage could be obtained.Accordingly, materials of the present invention can be considered aspreferable for thin-film capacitor.

Further, since surface smoothness property was superior, they can bepreferable thin-film material for manufacturing multilayer structure.

EXAMPLE 5

In the same way as example 1, Curie point of SBTT thin-film and electriccharacteristics(dielectric constant, tan δ and the loss Q value) ofthin-film capacitor sample were evaluated except for the followings. Assource material for pulsed laser deposition method,Sr_(X)Bi_(4−X)Ti_(3−X)Ta_(X)O₁₂(SBTT) sintered body(This sintered bodyis expressed by formula: Bi₂A_(m−1)B_(m)O_(3m+3) wherein symbol “m”=3,symbol “A₂”=Sr_(X), Bi_(2−X) and symbol “B₃”=Ti_(3−X), Ta_(X). Here, “x”is changed to 0.4, 0.6, 0.8, 1.0 and 1.2.) was used and about 50 nm filmthickness of SBTT thin-film(dielectric thin-film) was formed. Theresults are shown in Table 3.

Further, Curie point(Unit is ° C.) of dielectric thin-film is obtainedby temperature change of dielectric constant.

TABLE 3 Composition Curie Point Dielectric The Loss Q (x =) (° C.)Constant tan δ Value Ex. 5 0.4 500 150 <0.02 >50 Ex. 5 0.6 350 170<0.025 >40 Ex. 5 0.8 200 200 <0.05 >20 Ex. 5 1.0 50 250 <0.02 >50 Ex. 51.2 <−55 220 <0.01 >100

As shown in Table 3, when composition “x” for c-axis orientation film ofSBTT increased, Curie point decreased and dielectric constant at ambienttemperature(25° C.) increased. When composition “x” was about 1, Curiepoint was around ambient temperature, and dielectric constant at ambienttemperature was at maximum. Accordingly, when composition “x” was about1 or more, it became paraelectric phase at ambient temperature that theloss Q value increased. Namely, it was confirmed that, when highcapacitance was required, composition range of 1.0<x<1.2 was suitable.

EXAMPLE 6

In the same way as example 1, Curie point of LBT thin-film and electriccharacteristics(dielectric constant, tan δ and the loss Q value) ofthin-film capacitor sample were evaluated except for the followings. Assource material for pulsed laser deposition method, rare-earth elementof La added La_(X)Bi_(4−X)Ti₃O₁₂(LBT) sintered body(This sintered bodyis expressed by formula: Bi₂A_(m−1)B_(m)O_(3m+3) wherein symbol “m”=3,symbol “A₂”=Bi_(2−X), La_(X) and symbol “B₃”=Ti₃. Here, “x” is changedto 0, 0.4, 0.6, 0.8, 1.0, 1.2 and 1.4.) was used and about 50 nm filmthickness of LBT thin-film(dielectric thin-film) was formed. The resultsare shown in Table 4.

TABLE 4 Composition Curie Point Dielectric The Loss Q (x =) (° C.)Constant tan δ Value Ex. 6 0 700 140 <0.02 >50 Ex. 6 0.4 500 150<0.02 >50 Ex. 6 0.6 400 160 <0.02 >50 Ex. 6 0.8 300 180 <0.025 >40 Ex. 61.0 150 200 <0.05 >20 Ex. 6 1.2 0 240 <0.01 >100 Ex. 6 1.4 <−55 210<0.005 >200

As shown in Table 4, when composition “x” for c-axis orientation film ofLBT increased, Curie point decreased and dielectric constant at ambienttemperature(25° C.) increased. When composition x was about 1.2, Curiepoint was around ambient temperature, and dielectric constant at ambienttemperature was at maximum. Accordingly, when composition x was about1.2 or more, it became paraelectric phase at ambient temperature thatthe loss Q value increased. Namely, it was confirmed that, for needs ofhigh capacitance, composition range of 1.0<x<1.4 was suitable.

EXAMPLE 7

First, SrTiO₃ single crystal substrate(thickness of 0.3 mm) 4 a(See FIG.2, the same for following), which was [100] oriented, was prepared. Andon the substrate 4 a, by masking with metal mask of given pattern, withpulsed laser deposition method, 100 nm film thickness of CaRuO₃ madeelectrode thin-film as internal electrode thin-film 24 wasformed(pattern 1).

Second, with pulsed laser deposition method, on the whole surface ofsubstrate 4 a including internal electrode thin-film 24, SBTT thin-filmas dielectric thin-film 8 a was formed in the same way as example 1,except film thickness was 100 nm. When crystal structure of this SBTTthin-film was measured by X-ray diffraction(XRD), it was confirmed thatthis crystal structure was [001] oriented, that is, oriented to c-axis.Surface roughness(Ra) of the SBTT thin-film was, by measuring in thesame way as example 1, 0.5 nm that was superior in surface smoothnessproperty.

Third, on the SBTT thin-film, by masking with metal mask of givenpattern, with pulsed laser deposition method, 100 nm film thickness ofCaRuO₃ made electrode thin-film as internal electrode thin-film 26 wasformed(pattern 2).

Forth, with pulsed laser deposition method, on the whole surface ofsubstrate 4 a including internal electrode thin-film 26, SBTT thin-filmas dielectric thin-film 8 a was formed again in the same way as example1, except film thickness was 100 nm.

By repeating these processes, 20 layers of SBTT thin-film werelaminated. And the surface of dielectric thin-film 8 a arranged at themost external part was covered with protection film 30 which is composedof silica to obtain capacitor body 22.

Next, at both ends of the capacitor body 22, a pair of externalelectrodes 28 and 29 composed of Ag is formed to obtain rectangularparallelepiped configuration of thin-film multilayer capacitor samplehaving length of 1 mm×width of 0.5 mm×thickness of 0.4 mm.

Electric characteristic(dielectric constant, dielectric loss, Q value,leak current and short ratio) of obtained capacitor sample wereevaluated in the same way as example 1. The results were 250 dielectricconstant, 0.01 tan δ, 100 loss Q value and 1×10⁻⁷ A/cm² leak current andwere satisfactory. Further, temperature characteristic of dielectricconstant for capacitor sample was evaluated in the same way as example 1and its temperature coefficient was 190 ppm/° C.

EXAMPLE 8

In the same way as example 6, capacitor sample was manufactured andelectric characteristics(leak current and short ratio) of the capacitorsample were evaluated. The results are shown in Table 5.

TABLE 5 Composition Leak Current Short Ratio (x =) (A/cm²) (%) Ex. 7 0 1× 10⁻⁷ 10 Ex. 7 0.4 5 × 10⁻⁸ 5 Ex. 7 0.6 4 × 10⁻⁸ 5 Ex. 7 0.8 4 × 10⁻⁸ 5Ex. 7 1.0 5 × 10⁻⁸ 5 Ex. 7 1.2 5 × 10⁻⁸ 5 Ex. 7 1.4 5 × 10⁻⁸ 5

As shown in Table 5, when composition “x” for c-axis orientation film ofLBT increased, leak current decreased and short ratio decreased. Namely,it was confirmed that, in order to improve leak characteristic,composition range of 0.4<x<1.4 was suitable.

EXAMPLE 9

In the present invention, thin-film capacitor sample manufactured atexample 1, frequency characteristic and voltage characteristic wereevaluated.

Frequency characteristic was evaluated as following. At the capacitorsample, by changing frequency from 1 kHz to 1 MHz at ambienttemperature(25° C.), electrostatic capacity was measured and alsodielectric constant was calculated. The results are shown in FIG. 3. Forthe measurement of electrostatic capacity, LCR meter was used. As shownin FIG. 3, even changing frequency to 1 MHz at specific temperature, itwas confirmed that dielectric constant value does not change. Namely, itwas confirmed that frequency characteristic is superior.

Voltage characteristic was evaluated as following. At the capacitorsample, by changing metering voltage(impressed voltage) at specificfrequency(100 kHz) from 0.1V(50 kV/cm electrolytic strength) to 5V(250kV/cm electrolytic strength), electrostatic capacity wasmeasured(Metering temperature was 25° C.) at specific voltage and alsodielectric constant was calculated. The results are shown in FIG. 4. Forthe measurement of electrostatic capacity, LCR meter was used. As shownin FIG. 4, even changing metering voltage to 5V at specific frequency,it was confirmed that dielectric constant value does not change. Namely,it was confirmed that voltage characteristic is superior.

EXAMPLE 10

Heating single crystal silicon (100) substrate at 600° C., on thesubstrate, by pulsed laser deposition method and using Bi₄Ti₃O₁₂(Below,also as BiT) sintered body(This sintered body is expressed by formula:Bi₂A_(m−1)B_(m)O_(3m+3) wherein symbol “m”=3, symbol “A₂”=Bi₂ and symbol“B₃”=Ti₃.) as source material, about 50 nm film thickness of BiTthin-film(high dielectric constant insulating film) was formed.

When crystal structure of this BiT thin-film was measured, in the sameway as example 1, by X-ray diffraction(XRD), it was confirmed that thiscrystal structure was [001] oriented, that is, its c-axis orientationwas vertical to the surface of single crystal silicon substrate.Further, surface roughness(Ra) of this BiT thin-film was measured in thesame way as example 1.

Further, electric characteristics(dielectric constant, tan δ, the loss Qvalue, leak current and short ratio) and temperature characteristic ofdielectric constant for this high dielectric constant insulating filmcomprising this BiT thin-film were evaluated in the same way asexample 1. The results are shown in Table 6.

TABLE 6 Film Surface Leak Break-down Thickness Roughness Current VoltageDielectric Temperature The Loss (nm) Ra (nm) (A/cm²) (kV/cm) ConstantCoefficient(ppm/° C.) tan δ Q Value Ex. 10 50 2 1 × 10⁻⁷ >500 100 <±300<0.02 >50 Ex. 12 50 1 5 × 10⁻⁸ >1000 200 <±200 <0.01 >100

EXAMPLE 11

In the same way as example 10, dielectric constant and leak current forhigh dielectric constant insulating film were obtained except for thefollowings. As source material for pulsed laser deposition method,rare-earth element of La added La_(X)Bi_(4−X)Ti₃O₁₂(LBT) sinteredbody(This sintered body is expressed by formula: Bi₂A_(m−1)B_(m)O_(3m+3)wherein symbol “m”=3, symbol “A₂”=Bi_(2−X), Lax and symbol “B₃”=Ti₃.Here, “x” is changed to 0, 0.2, 0.4 and 0.6.) was used and about 50 nmfilm thickness of LBT thin-film(high dielectric constant insulatingfilm) was formed. The results are shown in Table 7.

TABLE 7 Dielectric Leak Current Composition Constant (RT) (A/cm²) (x =)@ 100 kHz @ 1 V Ex. 11 0 100 1 × 10⁻⁷ Ex. 11 0.2 105 5 × 10⁻⁸ Ex. 11 0.4110 3 × 10⁻⁸ Ex. 11 0.6 120 3 × 10⁻⁸

As shown in Table 7, it was confirmed that, as content of rare-earthelements at LBT thin-film(high dielectric constant insulating film)increased, dielectric constant increased and leak current decreased.Namely, it was confirmed that, high dielectric constant insulating filmof the invention is suitable for a gate insulating film.

EXAMPLE 12

On the surface of lower electrode thin-film, by pulsed laser depositionmethod and using Ba₂Bi₄Ti₅O₁₈(Below, also as B₂BT) sintered body(Thissintered body is expressed by formula: Bi₂A_(m−1)B_(m)O_(3m+3) whereinsymbol “m”=5, symbol “A₄”=Ba₂, Bi₂ and symbol “B₅”=Ti₅.) as sourcematerial, about 50 nm film thickness of B₂BT thin-film(high dielectricconstant insulating film) was formed.

When crystal structure of this B₂BT thin-film was measured by X-raydiffraction(XRD), it was confirmed that this crystal structure was [001]oriented, that is, its c-axis orientation was vertical to the surface ofSrTiO₃ single crystal substrate. Further, surface roughness(Ra) of thisB₂BT thin-film was measured in the same way as example 1.

Further, electric characteristics(dielectric constant, tan δ, the loss Qvalue, leak current and short ratio) and temperature characteristic ofdielectric constant for this high dielectric constant insulating filmcomprising this B₂BT thin-film were evaluated in the same way asexample 1. The results are shown in Table 6.

Note that embodiments and examples of the present invention wereexplained above, however, the present invention is not limited to theabove embodiments nor examples and may be modified in various wayswithin the scope of the invention.

1. A thin-film capacitance device composition including a bismuthlayer-structured compound whose c-axis is oriented vertically to asubstrate surface, wherein said bismuth layer-structured compound isexpressed by a formula: Bi₂A_(m−1−x)Re_(x)B_(m)O_(3m+3), wherein symbol“m” is selected from odd numbers, symbol “x” is 0.4 to 1.8, symbol “A”is at least one element selected from Na, K, Pb, Ba, Sr, Ca and Bi,symbol “B” is at least one element selected from Fe, Co, Cr, Ga, Ti, Nb,Ta, Sb, V, Mo and W, and symbol “Re” is at least one rare-earth elementselected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,Yb and Lu.
 2. The thin-film capacitance device composition as in claim1, characterized in degree of c-axis orientation for said bismuthlayer-structured compound is 80% or more.
 3. The thin-film capacitancedevice composition as in claim 1, wherein Curie temperature is −100° C.or more to 100° C. or less.
 4. The thin-film capacitance devicecomposition as in claim 1, wherein “m” in the formula composing saidbismuth layer-structured compound is anyone of 1,3,5 and
 7. 5. Thethin-film capacitance device composition as in claim 1, wherein said “x”in formula composing said bismuth layer-structred compound is 1.0 to1.4.
 6. A thin-film capacitance device comprising lower electrode,dielectric thin-film and upper electrode formed one by one on asubstrate, wherein said dielectric thin-film is composed of thin-filmcapacitance device composition, the thin-film capacitance devicecomposition include a bismuth layer-structured compound whose c-axis isoriented vertically to the substrate surface, and the bismuthlayer-structured compound is expressed by a formula:Bi₂A_(m−1−x)Re_(x)B_(m)O_(3m+3), wherein symbol “m” is selected from oddnumbers, symbol “x” is 0.4 to 1.8, symbol “A” is at least one elementselected from Na, K, Pb, Ba, Sr, Ca and Bi, symbol “B” is at least oneelement selected from Fe, Co, Cr, Ga, Ti, Nb, Ta, Sb, V, Mo and W, andsymbol “Re” is at least one rare-earth element selected from Sc, Y, La,Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.
 7. Thethin-film capacitance device as in claim 6, characterized in degree ofc-axis orientation for said bismuth layer-structured compound is 80% ormore.
 8. The thin-film capacitance device as in claim 6, wherein saidthin-film capacitance device composition has Curie temperature of −100°C. or more to 100° C. or less.
 9. The thin-film capacitance device as inclaim 6, wherein said substrate is composed of amorphous material. 10.The thin-film capacitance device as in claim 6, wherein thickness ofsaid dielectric thin-film is 5 to 1000 nm.
 11. The thin-film capacitancedevice as in claim 6, wherein “m” in the formula composing said bismuthlayer-structured compound is any one of 1, 3, 5 and
 7. 12. The thin-filmcapacitance device as in claim 6, wherein said lower electrode is formedby epitaxial growth on said substrate to[100] orientation.
 13. Thethin-film capacitance device composition as in claim 6, wherein said “x”in the formula composing said bismuth layer-structured compound is 1.0to 1.4.
 14. A thin-film multilayer capacitor comprising multipledielectric thin-films and internal electrode thin-films alternatelylayered on a substrate, wherein said dielectric thin-films are composedof thin-film capacitance device compositions, the thin-film capacitancedevice compositions include a bismuth layer-structured compound whosec-axis is oriented vertically to the substrate surface, and said bismuthlayer-structured compound is expressed by a formula:Bi₂A_(m−1−x)Re_(x)B_(m)O_(3m+3), wherein symbol “m” is selected from oddnumbers, symbol “x” is 0.4 to 1.8, symbol “A” is at least one elementselected from Na, K, Pb, Ba, Sr, Ca and Bi, symbol “B” is at least oneelement selected from Fe, Co, Cr, Ga, Ti, Nb, Ta, Sb, V, Mo and W, andsymbol “Re” is at least one rare-earth element selected from Sc, Y, La,Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.
 15. Thethin-film multilayer capacitor as in claim 14, characterized in degreeof c-axis orientation for said bismuth layer-structured compound is 80%or more.
 16. The thin-film multilayer capacitor as in claim 14, whereinsaid thin-film capacitance device composition has Curie temperature of−100° C. or more to 100° C. or less.
 17. The thin-film multilayercapacitor as in claim 14, characterized in said internal electrodethin-film is composed of noble metal, base metal or conductive oxide.18. The thin-film multilayer capacitor as in claim 14, wherein saidsubstrate is composed of amorphous material.
 19. The thin-filmmultilayer capacitor as in claim 14, wherein thickness of saiddielectric thin-film is 5 to 1000 nm.
 20. The thin-film multilayercapacitor as in claim 14, wherein “m” in the formula composing saidbismuth layer-structured compound is any one of 1, 3, 5 and
 7. 21. Thethin-film multilayer capacitor as in claim 14, wherein said internalelectrode thin-film is formed to [100] orientation.
 22. The thin-filmmultilayer capacitor as in claim 14, wherein said “x” in the formulacomposing said bismuth layer-structured compound is 1.0 to 1.4.
 23. Adielectric thin-film composition for capacitor including a bismuthlayer-structured compound whose c-axis is oriented vertically to asubstrate surface, wherein said bismuth layer-structured compound isexpressed by a formula: Bi₂A_(m−1−x)Re_(x)B_(m)O_(3m+3), wherein symbol“m” is selected from odd numbers, symbol “x” is 0.4 to 1.8, symbol “A”is at least one element selected from Na, K, Pb, Ba, Sr, Ca and Bi,symbol “B” is at least one element selected from Fe, Co, Cr, Ga, Ti, Nb,Ta, Sb, V, Mo and W, and symbol “Re” is at least one rare-earth elementselected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,Yb and Lu.
 24. The dielectric thin-film composition for capacitor as inclaim 23, characterized in degree of c-axis orientation for said bismuthlayer-structured compound is 80% or more.
 25. The dielectric thin-filmcomposition for capacitor as in claim 23, wherein said “x” in theformula composing said bismuth layer-structured compound is 1.0 to 1.4.26. The dielectric thin-film composition for capacitor as in claim 23,wherein Curie temperature is −100° C. or more to 100° C. or less.
 27. Athin-film capacitor comprising lower electrode, dielectric thin-film andupper electrode formed one by one on a substrate, wherein saiddielectric thin-film is composed of dielectric thin-film composition,the dielectric thin-film composition include a bismuth layer-structuredcompound whose c-axis is oriented vertically to the substrate surface,and the bismuth layer-structured compound is expressed by a formula:Bi₂A_(m−1−x)Re_(x)B_(m)O_(3m+3), wherein symbol “m” is selected from oddnumbers, symbol “x” is 0.4 to 1.8, symbol “A” is at least one elementselected from Na, K, Pb, Ba, Sr, Ca and Bi, symbol “B” is at least oneelement selected from Fe, Co, Cr, Ga, Ti, Nb, Ta, Sb, V, Mo and W, andsymbol “Re” is at least one rare-earth element selected from Sc, Y, La,Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu.
 28. Thethin-film capacitor as in claim 27, characterized in degree of c-axisorientation for said bismuth layer-structured compound is 80% or more.29. The thin-film capacitor as in claim 27, wherein said dielectricthin-film composition has Curie temperature of −100° C. or more to 100°C. or less.
 30. The thin-film capacitor as in claim 27, wherein said “x”in the formula composing said bismuth layer-structured compound is 1.0to 1.4.
 31. A high-dielectric constant insulating film including abismuth layer-structured compound whose c-axis is oriented vertically toa substrate surface, wherein, said bismuth layer-structured compound isexpressed by a formula: Bi₂A_(m−1−x)Re_(x)B_(m)O_(3m+3), wherein symbol“m” is selected from odd numbers, symbol “x” is 0.4 to 1.8, symbol “A”is at least one element selected from Na, K, Pb, Ba, Sr, Ca and Bi,symbol “B” is at least one element selected from Fe, Co, Cr, Ga, Ti, Nb,Ta, Sb, V, Mo and W, and symbol “Re” is at least one rare-earth elementselected from Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm,Yb and Lu.
 32. The high-dielectric constant insulating film as in claim31, characterized in degree of c-axis orientation for said bismuthlayer-structured compound is 80% or more.
 33. The thin-film capacitor asin claim 31, wherein said “x” in the formula composing said bismuthlayer-structured compound is 1.0 to 1.4.